MANILA - A civil engineer specializing in wind dynamics on Monday called the use of face shields in the fight against COVID-19 "redundant."

Engineer Joshua Agar of the University of the Philippines Diliman said face masks and physical distancing were sufficient to ensure that respiratory droplets would not spread from person to person.

"My opinion is that face masks are already enough in containing the production of respiratory droplets in the air," he told ANC's "Rundown."

"It already filters of what's coming out of your respiratory system, maybe that includes virus. Face shield is a redundancy," he added.

Re: face shields

As a researcher who simulate wind flows, I am puzzled with the insistence on face shields.

Face shields causes intake of air to the regions beneath the shield to induce higher negative pressures.

Higher negative pressure, higher particulate transport.

— Joshua C. Agar (@JoshuaCAgar) June 22, 2021

In his research, Agar said small respiratory particles could still make their way inside the shield at aerosol windspeed, allowing them to accumulate near the face, due to a negative pressure region it created beneath the shield.

He said face shields may even make people more vulnerable to the virus.

During a simulation using computational fluid dynamics, Agar said face shields could:

• Allow suction to the suspended particles into the head and face;
• Allow accumulation of the suspended particles near the face;
• And allow deposition of the suspended particles to the head and face.

"Basically what the face shield is doing is you're becoming a vacuum cleaner. When there's COVID in the air, you would be sweeping all the particles in the air base on the configuration on this face shield," he said.

For him, the risks of wearing face shields outweigh its benefits.

The US Centers for Disease Control and Prevention does not recommend wearing face shields for normal everyday activities or as a substitute for face masks.

"Face shields are not as effective at protecting you or the people around you from respiratory droplets," it said.

"Face shields have large gaps below and alongside the face, where your respiratory droplets may escape and reach others around you and will not protect you from respiratory droplets from others," it added.